The term Kaiserpfalz (German: [ˈkaɪzɐˌpfalts] ^ⓘ, "imperial palace") or Königspfalz (German: [ˈkøːnɪçsˌpfalts], "royal palace", from Middle High German phal[en]ze to Old High German phalanza from Middle Latin palatia [plural] to Latin palatium "palace") refers to a number of palaces and castles across the Holy Roman Empire that served as temporary seats of power for the Holy Roman Emperor in the Early and High Middle Ages.

The dukes and bishops of the empire also owned palaces, which were sometimes referred to as "pfalzen", especially since they were obliged to accommodate the emperor and his court when they were in transit, a duty referred to as Gastungspflicht (obligation to accommodate).

Kaiserpfalz is a German word that is a combination of Kaiser, meaning "emperor", which is derived from "caesar"; and Pfalz, meaning "palace", and itself derived from the Latin palatium, meaning the same (see palace). Likewise Königspfalz is a combination of König, "king", and Pfalz, meaning "royal palace".

Because pfalzen were built and used by the king as a ruler of the Kingdom of Germany, the correct historical term is Königspfalz or "royal palace". The term Kaiserpfalz is a 19th-century appellation that overlooks the fact that a king of Germany did not bear the title of the Holy Roman Emperor (granted by the Pope) until after his imperial coronation which required expeditions to Italy (Italienzug), which mostly were only undertaken years after his accession to the throne and in many cases not at all.

Like their peers in France and England, the medieval emperors of the Holy Roman Empire did not rule from a capital city, but had to maintain personal contact with their vassals on the ground. This was the so-called "itinerant kingship" or "itinerant court"; in German called Reisekönigtum ("travelling kingship").

The Merovingians in the Frankish Empire already ruled according to the feudal principle in which a ruler does not rule over a territory with specific land boundaries with the support of administrative officials, as in a territorial state, but rather his sovereignty was based on a personal relationship of dependence between feudal lords and their vassals (Personenverbandsstaat, a "personal dependency state"). Therefore, this dependency had to be constantly maintained and renewed, including through the allocation of positions or land. This was one of the reasons why kings and emperors constantly traveled around their realm and held Hoftage (court days, i. e. meetings with the powerful of the empire) and court sessions (to settle disputes and punish offenses to prove their authority) alternately in different parts of the country. A second reason was a lack of communication options over long distances at a time when there were often hardly any solid roads. Therefore, the court had to show its presence in order to keep the realm under control. A third reason was supply bottlenecks: Due to inadequate transport routes, it was not yet possible until the 13th century to provide long-term food supply for hundreds of people who had traveled to the same place, in addition to the local population. Consequently, instead of sending food to royal courts, the courts went to the food.

In France and England, where centralized states developed early, from the 13th century onwards, stationary royal residences began to develop into capitals that grew rapidly and developed corresponding infrastructure: the Palais de la Cité and the Palace of Westminster became the respective main residences. This was not possible in the Holy Roman Empire because no real hereditary monarchy emerged, but rather the tradition of elective monarchy prevailed (see: Imperial election, List of royal and imperial elections in the Holy Roman Empire) which led to kings of very different regional origins being elected. But if they wanted to control the empire and its often rebellious regional rulers, they could not limit themselves to their home region and their private palaces. As a result, kings and emperors continued to travel around the empire well into modern times. It was only King Ferdinand I, the younger brother of the then Emperor Charles V, who moved his main residence to the Vienna Hofburg in the middle of the 16th century, where most of the following Habsburg emperors subsequently resided. However, Vienna never became the official capital of the empire, just of a Habsburg hereditary state (the Archduchy of Austria). The emperors continued to travel to their elections and coronations at Frankfurt and Aachen, to the Imperial Diets (which developed from the “Hoftage”) at different places and to other occasions such as weddings, negotiations with other monarchs or military campaigns. The Perpetual Diet of Regensburg was based in Regensburg from 1663 to 1806. Rudolf II resided in Prague, the Wittelsbach emperor Charles VII in Munich.

Unlike the common notion of "palace", a pfalz was not a permanent residence but a place where the emperor stayed for a certain time, at most a few months; itineraries suggest that the monarch rarely would stay for longer than a few weeks, on mere transit stages often only a few days. Moreover, they were not always grand palaces in the accepted sense: some were small manor houses or fortified hunting lodges, such as Bodfeld in the Harz. But generally they were large manor houses (Gutshöfe), that offered catering and accommodation for the king and his companions, often running to hundreds of staff, as well as numerous guests and their staff and horses. For accommodation there were wooden outbuildings around the mostly stone main buildings. In Latin, such a royal manor was known as a villa regia or curtis regia. It is these expressions (and not pfalz) that are mostly mentioned in contemporary Latin documents. Unlike a pfalz, where the itinerant ruler stayed for a while and enacted his sovereign duties, a royal estate (Königshof) was just a farm with a smaller manor owned by the kingdom, which was occasionally used by the kings as a transit station. However, they were mostly mentioned in documents using the same Latin expressions.